Much attention is paid to semiconductor laser devices employing a package composed of a lead frame and a resin molding, because they are comparatively inexpensive and easy to mass-produce. However, such resin molding packages suffer from poor heat rejection in comparison with metal can packages that have conventionally been widely used. For this reason, resin molding packages are now used almost exclusively in infrared lasers having good temperature characteristics, and not in high-output lasers for CD-R/W drives, or in infrared lasers for DVD drives, or in blue or similar lasers requiring high operating voltages. An improvement on a resin molding package for better heat dissipation is proposed, for example, in Japanese Patent Application Laid-Open No. H11-307871. According to this proposal, the portion of a lead on which a laser element is mounted is made thicker, and the lead is enclosed in a resin with that portion exposed on the bottom face of the resin.
However, even when only the portion of the lead on which the laser element is mounted is made thicker as described above, a semiconductor laser device is seldom built into a pickup device in such a way that the thicker portion of the lead is kept in contact with some part of (the body of) the pickup device during actual use. Thus, the above-mentioned improvement does not contribute much to better heat rejection. Moreover, when the lead is completely enclosed in the resin, the positioning of the semiconductor laser device needs to be done with respect to the resin, which is unstable as a reference for positioning. Moreover, the thicker portion of the lead lies only in part of the width of the semiconductor laser device, and thus does not contribute much to increasing the mechanical strength of the semiconductor laser device. Moreover, since the thicker portion of the lead is exposed on the reverse face of the resin as described above, the resin on the reverse face needs to be made so thin as not to hinder the exposure of the thicker portion of the lead. This makes it difficult to increase the strength with which the lead is fixed. Moreover, to allow the lead to be exposed on the reverse face of the resin, the thicker portion of the lead needs to be elevated considerably relative to the other portion thereof, and in addition the thick portion has only a small area. This results in the semiconductor laser device having poor flatness, making its handling difficult and its setting unstable.
When such a semiconductor laser device is built into an optical pickup device or the like, the former is usually set in the latter by inserting the package of the former in that direction in which it emits laser light. During this insertion, the resin portion of the semiconductor laser device often interferes with, or is caught at, the rim of the opening formed in the body of the optical pickup device to allow the insertion.
A conventional example of this type of semiconductor laser device is disclosed, for example, in Japanese Patent Application Laid-Open No. H6-45703. This publication discloses a lead, a laser element mounted on the lead, and a resin frame for protecting the laser element. Here, part of the top edge of the lead and the two side edges thereof are used as reference portions for fitting.
However, in the semiconductor laser device described above, a resin leak occurs at that part of the top edge of the lead which is used as a reference portion for fitting, and, quite disadvantageously, this makes this reference portion for fitting inaccurate. The inventors of the present invention investigated the cause of such a resin leak, and have found out that, because the outer profile of the resin frame is located outside the top edge of the lead, the resin leaks into a punching sag formed in a lead frame when it is punched out.
Moreover, in the semiconductor laser device described above, the laser element is placed at the tip end of the lead to prevent laser light from being reflected on the surface of the lead. Disadvantageously, this increases the risk of the laser element coming into contact with a finger or tweezers when it is handled.
FIG. 14 shows the conventional semiconductor laser device described above in a state observed in its fabrication process. In FIG. 14, a first lead 100, a second lead 101, and a third lead 102 are each connected, at one end, to an outer frame 103. A tie bar 104 is connected to a midpoint of each of the first, second, and third lead 100, 101, and 102.
A light-receiving element 105 is mounted near the tip end of the first lead 100, a laser element 106 is mounted on the light-receiving element 105, and necessary wiring (not shown) is strung. A resin frame 107 is so formed as to surround the laser element 106 and keep the first, second, and third leads 100, 101, and 102 fixed at the other end. When the tie bar 104 is cut in portions indicated as “a,” “b,” “c,” “d,” and “e,” a semiconductor laser device 108 is obtained.
However, as described above, in this semiconductor laser device 108, after the tie bar 111 is cut, traces 111 and 113 thereof remain at a location 110 opposite to a reference portion 109 and at a location 113 opposite to a reference portion 112, respectively. Thus, when the semiconductor laser device 108 is inserted in a bracket (not shown) and pressed at the locations 110 and 113 with jigs, the tie bar traces 111 and 114 degrade the accuracy of fitting. This is the first disadvantage.
To overcome this disadvantage, the inventors of the present invention have abolished the link of the tie bar at the locations “a” and “e.” With this configuration, however, when the outer frame 103 is fed over a predetermined distance on a machine before the tie bar is cut, the vibration of the feeding or the like causes, for example, the tip portion of the first lead 100 to incline in a direction indicated as G1 or G2. As a result, in an energizing test, a test probe deviates from where it is supposed to touch. This is the second disadvantage.
Moreover, a window 115 is formed in the resin frame 107 in front of the laser element 106, making the laser element 106 more likely to come into contact with a finger or tweezers. This is the third disadvantage.